What is PPP? What is SLIP?

The Point-to-Point Protocol (PPP) and Serial Line Internet Protocol (SLIP) are ways of encapsulating data for transmission over a single serial interface, typically a personal computer connected by phone line to a server or PoP. PPP is usually preferred over the earlier de facto standard SLIP because it can handle synchronous as well as asynchronous communication. It also provides better security and data compression. PPP can share a line with other users and it has error detection that SLIP lacks. Because of all of these advantages, SLIP has fallen into disuse, but the basics of routing all information from a client to a single "gateway" server across a serial connection are the same.

PPP uses the Internet Protocol (IP) to route data between the server and the client. When a user dials into one of our PoPs, their computer is assigned an IP and a Gateway (the IP of the ARC they are connected to). All TCP/IP traffic to and from the client computer is sent via PPP directly to the Gateway for routing across the Internet. Essentially, PPP packages your computer's IP packets into a series (hence the term "serial") of 1's and 0's and forwards them to the server in order. (Obviously, the actual encapsulation is far more complicated than this). There, they can be put back into TCP/IP packets and routed across the Internet.

PPP is sometimes considered a member of the TCP/IP suite of protocols. Relative to the Open Systems Interconnection (OSI) reference model, PPP provides layer 2 (data-link layer) service. PPP is a full-duplex protocol that can be used on various physical media, including twisted pair or fiber optic lines or satellite transmission. It uses a variation of High Speed Data Link Control (HDLC) for packet encapsulation.